Expandable coaxial line connector



March 25, 1958 w. M. HALL EXPANDABLEI COAXIAL LINE CONNECTOR Filed Bed.

ML W H 7 w. 7 M A M M Y L .6 M

EXPANDABLE CGAXIAL LlNE CQNNE'CTQR William M. Hall, Lexington, Mass, assignor to Raytheon Manufacturing Company, Newton, Mass, a corporahon of Delaware Application December 13, 1952, Serial No. 325,327

1 Claim. (Cl. 333-97) This invention relates to expandable coaxial line connectors, and more particularly to connectors of this type that permit a coaxial line to be lengthened without appreciably attecting the impedance of the line over a broad band of very high radio frequencies.

In certain applications of coaxial lines designed to carry a broad band of very high radio frequencies, it is necessary for mechanical or other reasons to change the length of the coaxial line without interfering with the ability of the line to transmit a wide band of very high radio frequencies. in the simplest form of such a connector, overlapping spring pressure joints are formed in both the outer and inner conductors of both sections of the line. With this arrangement, the inner diameter of the outer conductor and the outer diameter of the inner conductor are different in the two sections, changing the ratio between these diameters and producing a sharp discontinuity in the impedance of the line. This discontinuity causes reflection of energy and other losses that are undesirable. As the length of the line is changed, the position of the discontinuity is shifted, causing additional difliculties.

By the construction of this invention, the two sections of the outer conductor are telescoped and the diameter of the central conductor of one section is increased to retain the same ratio to the inner diameter of the outer conductor as prevails in the rest of the line. The outside diameter of the first section of the inner conductor is tapered down to the outer diameter of the second section of the inner conductor to avoid a discontinuity at the point where they meet. The first section of the inner conductor is formed with an annular opening to receive the tubular end of the second section of the inner conductor. The central part of the first section of the central conductor is enlarged at its tip and slit to force the tubular end of the second section outward against the inner wall of the annular opening in the end of the first section or" the central conductor to form a good mechanical and electrical connection with it. Such a connector produces the minimum of discontinuities in the line and the band width and characteristic impedance of the line remain substantially the same over the range of movement of the joint.

Other and further advantages of this invention will be apparent as the description thereof progresses, reference being had to the accompanying drawings wherein:

Fig. l is a longitudinal section of a coaxial line conneo tor embodying the invention;

Fig. 2 is a section taken along the line 2-2 of Fig. 1; and

Fig. 3 is a section taken along the line 33 of Fig. 1.

In Fig. l, the reference numeral 16 indicates generally a section of coaxial line joined to an expandable section 11 by a standard type connector 2.2. The expandable section 11 comprises a first section 13 and a second section 14 of outer tubular conductors. The first section 13 has an outer diameter such that the second section 14 fits over it, making a sliding electrical contact. Slots 15 are formed in the end of the first section 13 of the outer conductor and the resulting fingers sprung outward to increase the pressure between the two sections, thus improving the electrical contact. The first section 16 of the center conductor is initially solid but is hollowed out 2,828,471 i atented Mar. 25, 1958 at the end to form a tube 17. A rod 18 of conductive material is inserted into the center of this tubular portion 1'7 and fastened in place by a pin 20. The rod 18 has a ball-shaped tip 21 with a slot 22 formed in it. The second section 23 of the center conductor is also initially solid but is hollowed out at its end to form a tube 24 formed with slits 24a. The walls of this tube 24 are tapered down to a knife edge 25. The sliding connector section 11 of tube is connected to a second section of coaxial cable 26 of standard construction by a second standard type connector 27. It will be noted that the first section of the central conductor 16 increases in diameter at the point 28 where it begins to extend beyond the first section of the outer conductor 13. This is for the purpose of maintaining the ratio between the outer diameter of the inner conductor and the inner diameter of the outer conductor constant as the inner diameter of the outer conductor increases from that of the first section 13 to that of the second section 14. This avoids the discontinuity that would otherwise appear at this point. It will also be noted that the tubular portion 17 of the first section of the inner conductor 16 is tapered from the point 28 to its end at a point 30 over the ball 21. This construction avoids a discontinuity at the point 30.

In operation when the sections are assembled, the knife edge 25 of the tubular part 24 of the second section of the inner conductor passes between the slit ball 21 on the end of the rod 13 and the tubular portion 17 of this conductor. The action of the hall 21 on the tube 24 makes a good mechanical and electrical connection between the two sections 16 and 23 of the center conductor While permitting relative movement of the two sections. The second section 14 of the outer conductor slips over the slitted first section 13 of the outer conductor to make a good sliding mechanical and electrical connection between the two sections of the outer conductor. This construction results in a section of coaxial cable that can be changed in length over an extended range without affecting the characteristic impedance of the coaxial line over a broad band of very high radio frequencies.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. it is, accordingly, desired that the appended claim be given a road interpretation commensurate with the scope of the invention within the art.

What is claimed is:

A coaxial line comprising an outer tubular conductor formed in two sections one fitting over the other with a resilient sliding contact, a center conductor formed in two sections, one section terminating in an enlarged portion protruding from the first section of the outer conductor, this protruding portion having a diameter enlarged by an amount required to maintain the ratio of the diameters of the inner and outer conductors of the coaxial line constant, the enlarged portion of the first section of the inner conductor formed as a tube with a central concentric rod formed with a split enlarged tip, the second section of the center conductor terminating in a tube with the walls tapered at the outer end and dimensioned to slide over the enlarged split end of the first section of inner conductor and within the tubular portion of the first section of the inner conductor.

References titted in the file of this patent UNITED STATES PATENTS 2,452,912 Dow NOV. 2, 1948 2,553,811 Carnine et al May 22, 1951 2,644,028 Bernet June 30, 1953 FOREIGN PATENTS 233,273 Switzerland July 15, 1944 

